Before buying, determine whether or not or no longer you need a high-temperature delivery or a low-temperature delivery temperature start: When the temperature reaches the set temperature, turn on the flexibility to start the device. (For example, when it reaches eighty degrees, switch on the flexibility of the circulating pump)Low temperature start: When the temperature reaches the set temperature, deliver to an end the ability to show off the device. (eg, attain 80 degrees, flip off the heater)The threaded interface is a 4-point outdoors thread interface. The diameter of the external thread is about 20mm.